Controller Area Network (CAN) buses allow microcontrollers to communicate with one another without being attached to a main computer. The CAN buses communicate with one another with a message based protocol to send and receive information between the multiple devices connected to the network. Originally, CAN buses were developed for the automotive industry, but have expanded their use into many other industries including entertainment and sporting uses.
CAN buses are usually connected serially with one another using a two wire system. These two wires, usually twisted, allow the multiple CAN buses to communicate with one another. The CAN transceiver of each individual CAN bus is connected to this two line system. Because this two wire system effectively allows for data signals to flow between the multiple CAN buses, proper termination is needed at the ends of the two wires connecting the multiple buses.
Electrical termination is necessary for proper communication between the multiple CAN buses. At the end of the chain of CAN buses a terminator is needed to prevent the electrical data signals from being reflected back causing interference with latter electrical communication. Terminator circuits are placed at the ends of the transmission lines and designed to match the electrical impedance of the network so that there is minimal signal reflection.
Termination circuits have been developed in the past to terminate the signals flowing out of CAN buses. In United States Published Patent Application No. 2009/0292841 A1 a network is disclosed communicating on a Local Interconnected Network (LIN) protocol. A CAN bus as part of this network has an output connected to a termination circuit configuration before continuing on to a sensor. In such a configuration LIN provides a cost effective transmission network for simple sensor applications. However in complex engine environments connecting multiple electronic control units, a different communication protocol is needed. Additionally, in these complex engine environments proper housing for a termination circuit is desired to make sure the termination circuit does not malfunction.
Proper termination circuits are especially important when dealing with complex engine signals and operations like those used in automotive, trucking, and locomotive engine environments. Engine environments such as these usually use a high speed CAN transmission protocol so that the multiple components of these engines can be in quick and proper communication with one another. Therefore, providing a stable and effective termination circuit at the ends of these CAN networks is of extreme importance to both provide correct communication within the network and to minimize electrical signal reflection and noise within the CAN network during operation.